Cloth draw-off apparatus

ABSTRACT

A cloth draw-off apparatus ( 10 ) for taking up a cloth ( 8 ) in a weaving machine is presented which includes two driven draw-in rollers ( 3, 5 ) around which the cloth is led, and optionally or as the case may be, a respective pressing roller ( 4, 6 ) to press the cloth against each of the two draw-in rollers.

The invention relates to a cloth take-up or draw-off apparatus fordrawing-off a cloth in a weaving machine in accordance with the preambleof claim 1 and to a weaving machine with a cloth draw-off apparatus ofthis kind.

High demands are nowadays being placed on the quality of cloth. Thisholds to a particular degree for technical fabrics, such as for examplefabrics for airbags in the automotive industry. In fabrics of this kindit is important among other things that the weft density be maintainedexactly. In order to achieve the required weft density, a comparativelyhigh fabric tension must be produced. This places stringent requirementson the cloth draw-off apparatus, since, on the one hand, the fabric,which enables a not very good purchase, i.e. is slippery, must not bedamaged and, on the other hand, must under no circumstances slip. Underthese requirements, conventional cloth draw-off apparatuses reach theirlimits in that they can not completely prevent the slippage of thefabric. As soon as the fabric slips, the weft density, which iscontrolled via the fabric draw-off, is no longer precisely correct. Inthe event of a temporary standstill of the weaving machine a slippingback of the fabric can lead to stop marks or in more severe cases evento damage to the machine.

A further problem arises when, as in the case of airbags, two fabriclayers are to be woven one above the other at the same time. If“drawing” takes place at only one of the fabric layers in the clothdraw-off apparatus, displacements between the fabric layers and thus thedevelopment of folds can occur. In this case the two fabric layers havedifferent weft densities, which can not be tolerated.

A conventional cloth draw-off apparatus is described in the patentspecification CH 619 497. The cloth draw-off apparatus describedincludes a fabric draw-off roller, which will be termed the draw-inroller in the following ing, about which the fabric is led, and adeflection roller which is pressed against the draw-in roller and whichwill be termed the pressing roller in the following. Furthermore, thecloth draw-off apparatus which is described in CH 619 497 includes anadditional fabric deflection point which is arranged between the breastbeam and the draw-in roller and close to the draw-in roller and pressingroller in order to increase the angle of wrap β with respect to thedraw-in roller. Through this measure a possible slippage of the fabricon the draw-in roller can be reduced. As explained in the previoussection, this measure does not suffice in all cases, however, in orderto completely eliminate the slippage of the fabric on the draw-inroller.

The object of the invention is to make available a cloth draw-offapparatus for drawing off a fabric in a weaving machine by means ofwhich a slippage of the fabric in the cloth draw-off apparatus isreduced or avoided. In addition, the cloth draw-off apparatus shouldalso be suitable for drawing off two-layered fabrics. A further objectof the invention consists in making available a weaving machine with acloth draw-off apparatus of this kind.

This object is satisfied in accordance with the invention by the clothdraw-off apparatus which is characterized in claim 1 as well as by theweaving machine which is characterized in claim 10.

The cloth draw-off apparatus for taking up a fabric in a weaving machineincludes a first driven draw-in roller around which the fabric is ledand in addition a second driven draw-in roller around which the fabricis led. The angle of wrap with respect to the draw-in rollers, i.e. theangle over which the fabric lies in contact on the draw-in rollers ineach case, is preferably as large as possible, for example between 100°and 356° and advantageously between 180° and 350°. In a preferredembodiment the cloth draw-off apparatus also includes at least onepressing roller in order to press the fabric against the first or seconddraw-in roller.

In a further preferred embodiment the first and second draw-in rollersare each connected to a driving means, for example to a drive shaftand/or a gear and/or to a chain sprocket, which are coupled to oneanother. The coupling can for example take place via respective chainsprockets and a chain. In a first variant the driving means are designedsuch that the draw-in rollers have the same direction of rotation, andin a second variant such that the draw-in rollers have oppositedirections of rotation. At least one of the two draw-in rollers ispreferably connected via a slip coupling or a frictional clutch to therespective driving means.

The second draw-in roller is preferably arranged at a distance from thefirst draw-in roller; and the draw-in rollers are preferably arrangedone above the other, with it being possible for one of the two draw-inrollers for example to be installed in the weaving machine in place of acloth beam.

In a further preferred embodiment the cloth draw-off apparatusadditionally includes a deflection roller or a deflection bar which isarranged in front of the first draw-in roller. The deflection roller ordeflection bar is preferably designed to have low friction, in that itis for example provided with a low friction coating, e.g. with a hardchromium layer, which can be matted or blasted.

In a further preferred embodiment the cloth draw-off apparatusadditionally includes a deflection apparatus which is arranged betweenthe first and second draw-in roller in such a manner that oppositelymoving fabric sections do not contact one another. In particular whenthe draw-in rollers are arranged one above the other the probability ishigh that on its way to the lower draw-in roller the fabric sectioncoming from the upper draw-in roller or the upper pressing roller makescontact with the fabric which is being led about the upper draw-inroller, which can lead to an undesirable frictional stress or, in thecase of a two layered fabric, to a mutual displacement of the fabriclayers, since the transport directions of the fabric sections at thepoint of contact are opposite to one another. Through the additionaldeflection apparatus between the first and the second draw-in rollers asituation can be prevented in which oppositely moving fabric sectionsmake contact with one another.

In a further preferred embodiment at least one of the pressing rollersis arranged substantially vertically above the respective draw-inroller. Thanks to the substantially vertical arrangement the pressingforce which is produced by the weight of the respective pressing rolleris a maximum. If the draw-in rollers are arranged one above the otherand the upper pressing roller is located substantially vertically abovethe upper draw-in roller, then a further force component, whichreinforces the pressing force of the upper pressing roller, arisesthrough the tension which acts on the fabric section between the firstand second draw-in rollers.

In addition the invention includes a weaving machine having a clothdraw-off apparatus in accordance with any one of the above describedembodiments.

The cloth draw-off apparatus in accordance with the invention has theadvantage that it reduces or avoids a slippage of the fabric in thecloth draw-off apparatus. In addition the development of folds in thecase of a two layered fabric can be reduced to an acceptable degree, forexample in that, as described, the fabric deflection is designed toinvolve low friction. Furthermore, the fabric can be cut after thedraw-off apparatus at any time without the weaving process beingdisturbed, which is advantageous, above all when no cloth beam and noexternal draw-off apparatus are provided to help the drawing-offoperation. The cloth draw-off apparatus in accordance with the inventioncan be formed from two individual cloth draw-off apparatuses which areadvantageously of the same design. For example two conventional clothdraw-off apparatuses, each with a draw-in roller and a pressing roller.This enables a simple and economical manufacture.

The above description of embodiments serves merely as an example.Further advantageous embodiments result from the subordinate claims andthe drawings. Moreover, individual features from the described orillustrated embodiments can also be combined with one another in thecontext of the present invention in order to form new embodiments.

The invention will be explained in the following in more detail withreference to the exemplary embodiment and with reference to thedrawings. Shown are:

FIG. 1 a schematic view of a weaving machine with an exemplaryembodiment of a cloth draw-off apparatus in accordance with the presentinvention, and

FIG. 2 a detail view of the exemplary embodiment of the cloth draw-offapparatus shown in FIG. 1.

In the view shown in FIG. 1 of a weaving machine with an exemplaryembodiment of a cloth draw-off apparatus in accordance with the presentinvention, the weaving machine includes a warp beam 15 from which warpthreads are unrolled, a back rest roller 14 at which the warp threadsare deflected, and a shed forming apparatus 13 by means of which a shed11 is formed through raising and lowering of the individual warpthreads. Furthermore, the illustrated weaving machine includes a reed 12in order to beat up a weft thread, which is inserted into the shed 11and which is not illustrated, up to the cloth edge. The thus formedfabric 8 is drawn off over a fabric support 1 by means of the clothdraw-off apparatus 10, with the cloth draw-off apparatus including twodriven draw-in rollers 3, 5, around which the fabric 8 is led. Theweaving machine which is shown in FIG. 1 is to be considered merely asan example. Modifications of the individual components and changes inthe illustrated arrangement are possible without departure from thecontext of the present invention. In the application shown in FIG. 1 thefabric 8 which is manufactured in the weaving machine is led to a batchwinder 21. This application is also merely an example.

FIG. 2 shows a detail view of the exemplary embodiment of the clothdraw-off apparatus in accordance with the present invention which isshown in FIG. 1. In FIG. 2 a fabric 8 is led over a fabric support 1 anda deflection roller or a deflection bar 2 to the cloth draw-offapparatus 10. The draw-off direction is marked in the drawing with anarrow 9. The cloth draw-off apparatus in accordance with the inventionincludes a first driven draw-in roller 3, around which the fabric isled, as well as additionally a second driven draw-in roller 5, aroundwhich the fabric is led. In an advantageous variant the draw-in rollers3, 5 are arranged at a distance from one another and can, for example,be arranged one above the other, as shown in FIG. 2. In an advantageousembodiment the cloth draw-off apparatus also includes a respectivelypressing roller 4, 6 in order to press the fabric against the respectivedraw-in roller 3, 5. The cloth draw-off apparatus 10 can for example beconstructed of two individual cloth draw-off apparatuses, each of whichcontains a draw-in roller 3, 5 and a pressing roller 4, 6. If no clothbeam is provided in the relevant weaving machine, the lower draw-inroller 5 can be installed in place of the cloth beam in an advantageousvariant.

In a further advantageous variant at least one of the pressing rollersis arranged substantially vertically above the respective draw-inroller. In FIG. 2 for example the upper pressing roller 4 is arrangedsubstantially vertically above the upper draw-in roller 3. The fullweight of the upper pressing roller is thus available for the pressingforce. The tension which the second draw-in roller 5 produces in thefabric can be used to additionally increase the pressing force of thefirst pressing roller 4, for example in that the second draw-in rolleris arranged beneath the first draw-in roller 3, as shown in FIG. 2.

In the exemplary embodiment the draw-in rollers 3, 5 are each connectedto a driving means, for-example to a drive shaft or a gear or to a chainsprocket, which are coupled to one another. The coupling of the drivingmeans and thus of the draw-in rollers can take place either purelymechanically, for example via two chain sprockets which are connected bya chain, or electronically through synchronization. In a first variantthe driving means are coupled in such a manner that that the draw-inrollers 3, 5 have the same direction of rotation, and in a secondvariant in such a manner that that directions of rotation of the draw-inrollers are opposite. In the case of opposite directions of rotation,for example in a two layered fabric, tension can be exerted once on theupper layer and once on the lower layer. In a further advantageousvariant the coupling between the driving means is designed so as not tobe rigid, for example in that at least one of the two draw-in rollers isconnected to the respective driving means via a slip coupling orfrictional clutch and/or in that at least one of the driving means isprovided with a frictional clutch.

As shown in FIG. 2, the cloth draw-off apparatus can comprise adeflection roller or a deflection bar 2 which is arranged in front ofthe first draw-in roller 3. In this case it is advantageous to designthe deflection roller or the deflection bar to have low friction, forexample in that the latter is provided with a low friction and/or slidecoating, such as for example a matted hard chromium layer. Furthermore,a deflection apparatus 7, for example in the form of a roller or a baror a section, can be provided in the cloth draw-off apparatus betweenthe first and the second draw-in rollers 3, 5 in order to avoid contactsbetween individual fabric sections. Without this deflection apparatus anundesirable frictional stress would occur at the points of contact,since the directions of movement of the fabric sections are normallyopposite at possible points of contact. The deflection apparatus 7between the first and the second draw-in roller is also advantageouslyof a low friction design.

The weaving machine with the cloth draw-off apparatus in accordance withthe invention is suitable for the manufacture of high quality fabrics,such as e.g. technical fabrics in which the weft density must bemaintained exactly. The thus equipped weaving machine is also suitablefor the manufacture of two layered fabrics, with the development offolds due to displacements between the fabric layers being low incomparison with conventional weaving machines. Particularly advantageousin addition is the simple installation of the cloth draw-off apparatusin accordance with the invention into a weaving machine if the latteralready has a first driven draw-in roller and the otherwise usual clothbeam is replaced by a second draw-in roller, about which the fabric isled. In this case the normally present cloth beam drive can be used as adrive for the second draw-in roller.

1. Cloth draw-off apparatus for drawing off a fabric in a weavingmachine, including a first driven draw-in roller around which the fabricis led, characterized in that the cloth draw-off apparatus also includesa second driven draw-in roller around which the fabric is led.
 2. Clothdraw-off apparatus in accordance with claim 1, including in addition atleast one pressing roller in order to press the fabric against the firstor second draw-in roller.
 3. Cloth draw-off apparatus in accordance withclaim 1, with the first and second draw-in rollers each being connectedto a driving means which are coupled to one another and/or which aredesigned such that the draw-in rollers have the same direction ofrotation.
 4. Cloth draw-off apparatus in accordance with claim 3, withthe driving means being designed such that the draw-in rollers haveopposite directions of rotation.
 5. Cloth draw-off apparatus inaccordance with claim 3, with at least one of the two draw-in rollersbeing connected via a frictional clutch to the respective driving means.6. Cloth draw-off apparatus in accordance with claim 1, with the seconddraw-in roller being arranged at a distance from the first draw-inroller, and/or with the draw-in rollers being arranged one above theother, and/or with one of the two draw-in rollers being installed in theweaving machine in place of a cloth beam.